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Re: Can't set lower MTU on gif?



John Klos <john%ziaspace.com@localhost> writes:

> create
> tunnel 2001:470:a068:5:250:baff:fecb:32e 2605:bc00:0:114:230:48ff:fe98:d1a8
> inet 192.80.49.75 192.80.49.74 netmask 255.255.255.254
>
> [snip
>
> However, NetBSD doesn't let the MTU for gif to be set to less than
> 1280 bytes:
>
> #define GIF_MTU_MIN     (1280)  /* Minimum MTU */
>
> Is there a good reason for this? If there is, then what's a better way
> to route IPv4 over IPv6 while avoiding this issue?

IPv6 requires that MTU be >= 1280.  However, I am pretty sure that's a
v6 rule. not general.   So it should be possible to set the MTU lower if
the inner protocol is limited to v4.

I would suggest just ifdefing' out the check and seeing how it goes.

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